Electroplating



Sept. 19, 1933. ,Y M. FIEDLER ETAL 1,927,162

-' u ELEGTROPLATING y Filed Feb. 27, 1931 2 Sheecs-Sheei'l l INVENTORS v 3 Sept. 19, 1933. M. FIEDLER Er AL ELECTROPLAT ING Filed Feb. 27, 1931 2 Sheets-Shea?l 2 www Patented Sept. 19, ,1933

PATENT OFFICE 1,921,162 ELEc'rnoPLA'rlNG Marcell Fiedler, Highland Pessl, New Brunswick, N. J.,

Research Corporation, poration of New York Application February 27,

12 Claims.

, This invention relates to a method and apparatus' for surface plating the interior surface of tubes and similar shapes by the electror deposition of chromium or other metals and in d particular the invention relates to plating relatively small diameter, long length pipe.

It has been substantially impossible to effectively plate the interior surface of long cylindrical tubes electrolytically because of the excessive formation of gases in the electrolyte, which gases hinder and prevent the satisfactory deposition of the metal.

One of the principal objects of this invention is to provide a method for effectively electroplating the internal surface of metallic pipe having a relatively long length and small diameter.

Another object of this invention is to provide l an apparatus for rapidly and completely electroplating the inside of long tubes in which the relation of the length to the diameter may be as great as 200 to 1 and the anodic shaft is coextensive in length with the tube.

Another object of this invention is to provide an apparatus for electro-plating the inside' of long tubes in which the current density and rate of deposition may be maintained constant.

Another object of this invention is to provide an apparatus to be used in the internal plating of metallic objects for rapidly removing the formed gases and maintaining the proper concentration of the electrolyte.

Another object of this invention is to provide an improved apparatus for plating the interior surface of substantially tubular members in which the temperature regulation is more readily maintained and in which the pipe may be suitably cleaned by a slight change of uid material and electrical connections.

Another object of this invention is to provide an apparatus for electroplating the interior of metallic objects in which the anode is rapidly revolved with respect to the cathode and the elec` trolyte is continuously passed through the object to be plated to maintain the rate of deposition, temperature of electrolyte and concentration of electrolyte constant and whereby the .gases formed may be rapidly removed to facilitate the plating.

Further objects and advantages of this invention will appear from the following description of a'preferred form -of apparatus in connection with the attached drawings which schematically illustrate such apparatus' and in which:

Figure 1 is a side elevation of a device for chromium plating long tubes.

Park, and Hubert assignors .to New York, N. Y., a. cor- 1931. Serial No. 518,670

section through the pipe Figure 2 is a vertical interior desupporting bearings, illustrating the tails of construction.

Figure 3 is a transverse section through the tube substantially on the line 3-3 of Figure 2.

Figures 4 and 5 are modifications of the anode shaft; and

Figure 6 is a modification of the anode shaft showing a different form of spacing means for maintaining the distance between the shaft and @5 metallic tube.

As shown in Figure l, the tubular pipe 10 to be internally chromium plated is mounted between two supports 12' and 14,-the support 14 being adjustable on the frame 16. A central anode shaft 18 of greater length than the pipe 10 is adapted to pass throughfthe pipe 10 as more clearly shown in Figure Zand isA provided with external commutator collars 19 and 19a with which copper brushes 20 and 20a cooperate. The pipe 10 is provided with suitable clamps 21 and 21a which are connected into the electric circuit together with the brushes 20 and 20a. Duplicate electrical connections are made on each end of the anode shaft 18 and the ends of the pipe 10 in order to more uniformly vmaintain the electrical current, the resistance'l ofz`cathode and anode thus being reduced-.v y

As shown in Figure 2, the pipe'10 to be plated is non-rotatably mountedwithin the supports 12 and 14 by means of bushings 12a and 14a and suitable packing 12b and 14h maintains the pipe in liquid-tight contact with the supports and at the same time insulate `the pipef from electrical contact with the support. vAdditional supports for the pipe l0 intermediate -itsjlength may bel used if required to prevent-sagging. Directly b'e-I hind the respective supports and adjacent the I ends of the pipe, pockets 12c`and14c,.are provided and with these pockets electrolyte conduits 23 95 and 24 communicate. Asthe'pockets 12e and' i 14e are normally sealed there is' thus an electrolytic chamber within the pipe-'.10' which is provided with the electrolyte supply-and discharge 100 conduits 23 and 24. 'A v 'i l The anode shaft 18 extends'through the pipe 10 and in substantial parallelism therewith. It is preferably of greater lengththan the pipe 10 to permit continuous plating of the v entire pipe at one time. The supports 12 and 14 act as bearings for the anode shaftat substantially the extreme ends thereof andy bushings 12d and 14d re. v spectively cooperate with the. ends of the anode shaft 18 to prevent any leakage through the bearing portions 12e and 14e`respectively. The bushand i4! respectively, which pockets are not in communication with the pockets 12e and 14e except by. such undesirable leakage as may escape through the bearing portions 12e and 14e.

The anode shaft 18 is preferably provided with a spiral insulator 32 which may be wound on the shaft substantially throughout its length through the tube or pipe 10. and may be of such diameter as to extend into close proximity to the pipe 10. Inasmuch as the distance between supports 12 and 14 often exceeds-l2 ieet and may be as great as 20 feet in length and as the anode shaft is of iron, or lead covered iron, andas the shaft is approximately outside diameter for a pipe 10 of i3" inside diameter, it has tendency to warp and the insulator prevents any short circuit due to such deflection. If the ratio of the diameter` of the pipe to the diameter of the anode is suiiiciently large. the anode could be made rigid enough so that its extreme deflection could not cause a short circuit in the pipe and insulators might not be necessary. In this case. lead coated iron blades to bring about the necessary centripetal force could be employed instead of insulators. The eccentricity. however, does not effect the plating as the rotation of the shaft always spaces it an equal distance-from the tube surface. The anode shaft 18 is also provided with a plurality of elongated slits 18a extending substantially the length of the shafts. The slits are also provided in the anode shaft 18 within the chambers 12f and laf affording an open communication between the4 chambers within the pipe 10 and the chambers 12j and 14] on the extreme ends of the pipe.

In operation, the anode `18 is rapidly rotated at approximately 1700 R. P. M. by the motor 33 which drives the pulley 34 on the end of the shaft 18. As the electrolyte is turned into the chamber within the pipe 10 and the anode shaft 18 is rotated at a high rate, the electric circuit is energized to create a flow of electricity between the anode 18 and the pipe 10 which becomes the cathode. The electricity flows through the' electrolyte and chromium is deposited on the interior surface of the pipe 10. This deposition will be uniform as the anode is constantly maintained at a uniform distance from the interior surface of the pipe due to its continuous rotation and the gases which are formed within the electrolyte are removed in the present construction by the extreme rapid rotation of the anode 10. Such rotation causes a centrifugal action on the dense electrolyte and the hydrogen gas which is relatively light is forcedinto the center of the chamber and in close contact with the revolving anode 18. As the anode is provided with a plurality of apertures 18a, the hydrogen will be driven into the apertures 18a Within the pipe 10 and may be withdrawn through the chamber 12f and 14j. The gas will not remain on the interior surface of the pipe to prevent a regular deposit of metal and the denser electrolyte will not pass into the vapertures 18a, thus maintaining the center of the anode substantially dry. The centrifugal action not only forces the gas in but keeps the electrolyte out and the gas is rapidly and completely removed from the chamber. Conduits 35 and 36 communicate with the chambers 12f and 14j, removing the gas from the anode shaft 18 andalso removing the small amount of leakage of electrolyte through the bearing portions 12e and 14e.

Referring to Figure 1, the conduit 23 communiings 12d and lad form. additional pockets l2! cates with a reverse valve 25 with which valve the conduit 2a also communicates. To afford an adequate source of supply of electrolyte. the tank 26 is provided and a pump 27 draws electrolyte through the pipe 28. discharging into the reverse valve 25. In one position of the control handle 29. the electrolyte will-pass through the conduit 23 into the chamber 12d through the interior of the pipe 10, out throughmthe chambenliof,

through the'condimto the valve 25, and the electrolyte will then discharge through the pipe 30 into the tank 26. By reversingv the handle 29, the electrolyte will be drawn from the tank 26 through the pump 27 into the valve 25 but this g time will be discharged through the pipe 24 into` the chamber 14e, through the pipe l0, out through the pipe 23, back to the valve 25 and will then be discharged through the pipe 30 back to the tank.

The valve 25 is of well known construction and is provided solely for the purpose of reversing the flow of electrolyte 'through the pipe 10.

The electrolyte is thus continuously circulated and the reversal of electrolyte takes place at intervals of approximately one-half hour. The circulation of the electrolyte additionally removes the gas which may be occluded in the electrolyte as the electrolyte in passing into the tank 26 is exposed to the air and releases any gas entrapped therein. The continuous flow of electrolyte also' controls the heat formed and the rate of the flow may be effectively controlled by valves so that the heat may be maintained uniform. The heat of the plating solution might be artificially maintained through the use of steam or water coils or by regulating room temperature or in any other desired manner. To effect uniform plating of the entire tube, the valve 29 is reversed at the end of a half-hour interval and the ilow through the tube .is in the reverse direction to the arrows shown in Figure 2.

Figure 4 shows a modified form of anode shaft which may be hollow or solid. If hollow, it is provided with apertures or slits 40a through which the gas will escape to the end chamber 12f and 14]. Such a shaft will be rotated in the direction of the arrows thus forming a slight,

vacuum adjacent the apertures 40a and additionally inducing the hydrogen bubbles to pass into the center to be removed. If the shaft were solid, the gas would be conducted along the groove and discharged at the bearings due to the centripetal pressure and formation of a vacuum by counter-clockwise rotation.

A slightly further modification of the anode shaft is shown in Figure 5 and this shaft 42 is likewise provided with openings 42a for the gas bubbles. This shaft will also be driven in the direction of the arrow and the pockets 43 formed by the V shape sides will induce the gases from the electrolyte. With any `of the forms of anode, it is, of course, desirable to provide the insulator material, such as shown in Figure 2 as the spiral 32, as this tends not only to promote circulation but also effectively prevents any contact between the anode and the cathode pipe.

In Figure 6 is shown a slight modification of supporting and spacing means 44 which is preferably an insulator member mounted in the anode shaft 18 by rivets 45. The insulator extends will also effectively prevent an electric short cir-- c uit within the plating chamber.

The electrolyte may be any of the usual and well known compositions of electrolyte for chromium plating such as 200 to 450 grams per liter radiation in the tank it can be kept at the preferredtemperature between 38 and 55 C. The

cathode is shown as a thin steel pipe and may be cleaned by a suitable alkali electrolytic cleaning compound by passing the current through the compound in the usual direction prior to the plating operation. If an acid is used for anodic cleaning, the current must be reversed.

Due to the rapid rotation of the anodic shaft there is a more uniform plating and deposition of metal on the pipe 10. This is due in part to the constant relation between the anodic shaft and the cathode pipe. During any small period of time the distance between the anode and the cathode is substantially constant and the surface relation of any portion of the anode is the same with respect to any portion of the inside of the pipe. Furthermore, as the anode extends beyond both ends of the pipe, the entire pipe is plated at once and without movement'of the anodein an axial direction. The pipe may thus be plated more rapidly and it is unnecessary to have additional mechanism to move the pipe axially. The anode being hollow also acts effectively to conduct the .gases from the plating chamber. The temperature of the electrolyte may be readily maintained constant, the current is subject to exact regulation and if the gas bubbles are rapidly removed and the distance and surface relation of the anode with respect to the cathode can be governed, a very high degree of eincency can be had. The plating is thus uniform in all respects. If the ratio of the anode to the cathode is insufficient it is possible to corrugate the anode thereby increasing its surface.

The rotation of the anode as particularly mentioned is the most convenient, practical method for bringing about a relative rotation between the anode and cathode. For the purpose of the invention, however, it would be equally as possible to rotate the cathode. Such rotation of the cathode might tend to increase the centrifugal effect of the electrolyte, although the rotation of the anode, as in the present instance either with a spiral insulator or the paddles as shown in Figure 6, acts satisfactorily to remove the gases and efciently plate the pipe. The support for the cathode is readily adjustable and can accommodate various lengths of cathode pipe within the limitation of the device. Pipes up to twelve feet in length have been effectively plated. As the formation of gas is dependent on the interior surface of the pipe, a large pipe could belonger and the ratio of 1 to 240 still maintained. There has been little difficulty in plating large diameter, short length pipes and the present invention relates particularly to the long length, small diameter pipes with ratios as high as 1 to 200 in diameter to length.

With such a device it is possible to bring about the most satisfactory plating conditions by maintaining the proper concentration and therefore the constant conductivity of the electrolyte; by maintaining the temperature constant; by the rapid removal of the gaseous products of the electrolytic reactions; and by maintaining a constant current density or rate of deposition. The rst of these is possible by the use of a pump or gravity flow circulating arrangement, the direction and velocity of which can be changed at will. The second feature is also controlled by the circulating system, it being understood that the temperature would tend to rise to an undesirable degree not only due to the electrolysis process but also due to the electric resistance of the anodic shaft.

The third feature, the removal of gaseous products is by means of the circulating of the electrolyte itself and/or the centripetal force as produced by the necessarily rapidly revolving anodic shaft which is hollow and provided with gas escape slots. The fourth feature, the maintenance of a constant current density or rate of deposition is possible by maintaining the distance between the cathode and anode constant and by maintaining the surface ratio of the cathode and the anode area constant by means of electrically insulating, acid resistant, spacing material and the rapid rotation of the anodic shaft.

These features could be similarly applied to the plating of a plurality of tubes simultaneously by having the electrolyte and supports common to all tubes and having independent anodesfor each tube, the anodes operating through a multiple head and being driven either from a common source and all geared together or being separately driven.

While we have shown a preferred form of embodiment of our invention and described the same with particular reference to chromium plating, it will be obvious that other metals can be plated in the same way and that modifications may be made in the apparatus and We, therefore, desire a broad interpretation of our invention within the scope of the claims appended hereinafter.`

We claim:

1. The method of plating the interior surface of long length, small diameter tubes which'comprises forming a chamber within the tube, passing electrolyte through said tube and revolving a coextensive anode Within said chamber and within said electrolyte while causing a ow of current between the anode and the tube and simultaneously withdrawing gases through said anode.

2. An apparatus for plating the interior of a long length, small diameter tube of the class described which comprises means for supporting the tube to be plated in a liquid-tight chamber, means to pass an electrolyte through said tube, a hollow anode mounted within said tube, means to cause rapid relative movement between said anode and said tube, and means to pass a plating current between the anode and the tube, said relative movement of said anode and pi'pe forcing formed gases into said anode, and means to remove the gases therefrom.

3. The method of removing gaseous products in the interior electro-deposition of metal which icomprises the rapid rotation of a hollow anodic shaft within the electrolyte in such manner to force the electrolyte against the interior surface of the pipe to be plated and to force the lighter gaseous products into the center of the anodic shaft.

4. `apparatus for plating the internal surface of long length, short diameter pipes whose ratio is substantially 200 to ll comprising a plurality of supports, a cathodic pipe mounted between said supports, means to forni an electrolytic chamber with said cathode, means to force electrolyte through said chamberfmeans to reverse the flow of electrolyte throughsaid chamber, an anodic shaft mounted Within said pipe, said shaft being hollow and having-:iaplurality of slots therein, means to rotate said shaft\to,cause a centrifugal action of said Ielectrolyte, and to force occluded gas through lsaidslots into the center of said anodic shaft and means to withdraw the gaseous products from the ends of said shaft.

5. Apparatus for plating the internal surface of long length, small diameter pipes whose ratio is substantially 200 to l, comprising supports for each end of the pipe, a cathodic pipe mounted between lsaid supports, means to form an electrolytic chamber with said pipe, means toforce electrolyte through said chamber, means to reverse the flow of electrolyte through said chamber, an anodic shaft mounted withiril said pipe,

said shaft being hollow and having a plurality of slots therein, means to rotate said shaft to cause a centrifugal action of said electrolyte, and to force occluded gas through said slots into the center of said anodic shaft and means to withdraw the gaseous products from the ends of said shaft, and means to pass an electric current between said anodic shaft.

6. The method of electro-plating the interior of tubular shapes and removing occluded gases therefrom, which comprises placing an anode inside the tube, insulating the tube from the anode, passing a plating current between the anode and tube, centrifugally forcing the'electrolyte against the inside of the tube and creating a lreduced pressure section adjacent the center of the tube, removing the gases from the reduced pressure section adjacent the center of the tube, and venting the gases outside of the tube.

7. The method described in claim 6, which comprises venting the gases through a hollow anode.

8. The method described in claim 6, which comprises rotating the anode and causing the gases to pass from the tube through the rotating anode.

9. In an electro-plating apparatus for internal plating of the class described, means to en= close a quantity of electrolyte, means to centrifugally force said electrolyte against the object to be plated, and means to remove. the gases through the centrifugal driving means, and means to remove the gases from said centrifugal driving means.

l0. An apparatus for plating the interior surface of tubular shapes which comprises means for supporting the tubular shape to be plated, means to form a liquid tight chamber therein, means to pass an electrolyte through said chamber, a hollow anodic shaft mounted within said tubular shape, means to rapidly rotate said shaft 90 with 'respect to said tubular shape, paddles mounted on said shaft causing a centrifugal movement of the electrolyte toward the tubular shape to be plated, said shaft having means by which the formed gases may be withdrawn from the electrolyte chamber.

, 11. An apparatus for plating the interior surface of tubular shapes which comprises means for supporting the tubular shape to be plated, means to form a liquid tight chamber therein, means to pass an electrolyte through said chamber, a hollow anodic shaft mounted within said tubular shape, means to rapidly rotate said shaft with respect to said tubular shape, said shaft being non-circular and having overhangs, said 05 overhanging portions creating a vacuum in rotation to withdraw the formed gases from the electrolyte chamber.

12. An apparatus for plating the interior surface of tubular shapes which comprises means for supporting the tubular shape to be plated, means to form a liquid tight chamber therein, means to pass an electrolyte through said chamber, a hollow anodic shaft mounted within said tubular shape, means to rapidly rotate said shaft 115 with respect to said tubular shape, said shaft having V shaped pockets, slits adjacent said pockets, and means to withdraw formed gases in said V shaped slits, one side of said V shaped pocket tending to set up centrifugal movement 120 of said electrolyte.

MARCELL- FIEDLER. HUBERT PESSL. 

